Equilibrium solubilities, oil-water partition coefficients and in vitro skin permeation features of two constituents in total alkaloids from Strychni Semen / 中成药

ABSTRACT

AIM To investigate the equilibrium solubilities,oil-water partition coefficients and in vitro skin permeation features of brucine and strychnine in total alkaloids from Strychni Semen.METHODS Saturated dissolution method was applied to determining the equilibrium solubilities of two constituents in ethanol (10％,20％,30％,60％,90％,anhydrous ethanol),trichloromethane,n-octanol and surfactants (0.5％ tween,0.5％ sodium deoxycholate,0.5％ oleic acid).Shake-flask method was adopted in detecting their oil-water partition coefficients in PBS (pH 2.5,4.0,5.0,5.8,6.8,7.0,7.4,9.0).Modified Franz diffusion cell method was used for evaluating their in vitro skin permeation features in PBS,20％ ethanol and anhydrous ethanol.RESULTS Both brucine and strychnine showed the highest equilibrium solubilities in trichloromethane and the lowest equilibrium solubilities in surfactants.The equilibrium solubility of strychnine was higher than that of brucine in ethanol (＞ 20％) or PBS (pH ＜ 8.0),which reached the highest in 60％ ethanol and pH 2.5 PBS,respectively.The similar oil-water partition coefficients of two constituents,proportional to pH value,reached the highest at pH9.0.And they exhibited the highest accumulated transdermal absorptivities in anhydrous ethanol and pH 9.0 PBS,respectively.CONCLUSION Solvent type has obvious effects on the equilibrium solubilities,oil-water partition coefficients and in vitro skin permeation features of both brucine and strychnine.This study can provide a reference for the bioavailability improvement of transdermal drug delivery and development of related preparations.